U.S. Rep. Steny H. Hoyer announced last week that he supports the right of same-sex couples to marry, one day after President Barack Obama did the same on national television.

“Because I believe that equal treatment is a central tenet of our nation, I believe that extending the definition of marriage to committed relationships between two people, irrespective of their sex, is the right thing to do and will not, in any way, undermine the institution of marriage so important to our society nor impose a threat to any individual marriage,” Hoyer (D-Md., 5th) said in a statement. “It will, however, extend the respect due to every one of our fellow citizens that we would want for ourselves and our children.”

The announcement marks a shift for the congressman, who had previously supported conferring the legal rights enjoyed by married couples to same-sex partners but reserving the term “marriage” for heterosexual unions.

“The word 'marriage' has held a specific meaning for centuries as the union between a man and a woman. But it has also meant, in a broader sense, a commitment of one person to another, recognized by each of them and by society,” Hoyer said in the statement. “I have believed that the phrase 'civil union' was an appropriate definition of a relationship that is both different and the same between two people of the same sex. And I have believed strongly that such couples must be treated equally under the law.”

Gov. Martin O'Malley (D) signed a bill legalizing same-sex marriage March 1, but Maryland voters will likely have the chance to decide the matter in November. Opponents expect to gather enough signatures to petition the bill to the 2012 ballot.

The divisive issue also has made national headlines in recent weeks. Vice President Joe Biden said he was “absolutely comfortable” with same-sex marriage in a May 6 appearance on NBC's “Meet the Press.”

Two days after that, North Carolina voters passed a constitutional amendment defining marriage as a union between one man and one woman, effectively banning gay couples from marrying in the state. Two days later, after years of describing his position on the issue as “evolving,” Obama announced his support for same-sex marriage during an interview on ABC.

Hoyer's newfound position puts him at odds with a significant chunk of his district on the issue. A majority of black and conservative voters, who each make up about one-third of Hoyer's “very safe Democratic district,” oppose legalizing gay unions, said Todd Eberly, a political science professor at St. Mary's of College of Maryland.

The same-sex marriage bill passed the overwhelmingly Democratic state legislature by narrow margins after several black lawmakers joined with Republicans in opposition.

“Conservatives who routinely vote against him will be even less fond of him,” Eberly said. “This could possibly drive a wedge between him and the African-American constituency that has been crucial to his success.”

While Obama might have had the incentive of wooing new, wealthy donors over his same-sex marriage announcement, “there is absolutely no political upside to Hoyer doing this,” Eberly said. “You have to look at what Hoyer said and say this is a principled stand, this is what he believes.”

One of the first votes Hoyer cast as a newly elected state senator in 1967 was to repeal a Maryland law prohibiting interracial marriage.

“It was a legacy of a discriminatory history of prejudice and segregation,” Hoyer said in his statement. “It was my feeling then and now that individuals have a right to choose their partners, and society must accord them that freedom.”

Hoyer called the debate over same-sex marriage “a variation of that miscegenation issue.”

Along with the latest round of congressional redistricting — which many black voters felt was used to protect the state's incumbent congressmen at the expense of minority representation — Hoyer's announcement now gives his opponent on the 2012 ballot, Del. Anthony J. O'Donnell (R-Calvert, St. Mary's), “two issues he can use to break down African-American loyalty to Steny Hoyer,” Eberly said.

As the leading Republican in the Maryland House of Delegates, O'Donnell is one of the more capable candidates Hoyer has ever faced.

But Eberly noted that in the 2010 election, a bad one for Democrats nationwide, Hoyer raked in 64 percent of the vote against a strong Republican challenger in Charles Lollar, himself an African-American. It was still the closest anyone had come to defeating Hoyer since 1996 and only the fourth time in 15 elections that Hoyer failed to claim at least 65 percent of the vote.

Eberly expects this year's race to be closer than Hoyer-Lollar was in 2010 but said the congressman's “margins are so large, he could stand to take a hit.”

“What this does is it gives O'Donnell a clear issue he can take to Hoyer's turf and it's an issue that hurts Hoyer when trying to come down here to O'Donnell's turf,” Eberly said. “Now, does this push O'Donnell over the top? Goodness no. ... My argument would be that Hoyer's margin is so large that this opening would not be enough to undermine Hoyer's re-election chances.”